Possible Clues:

• Tree of Madagascar
• Broad-trunked tropical tree
• Gigantic tropical tree with very thick trunk
• With 25-Across, it has a huge trunk
• Monkey bread source
• Old British seaman joins another climbing tree
• Tree with a gourdlike fruit
• Tree that's home to Rafiki in 'The Lion King'
• Madagascar tree
• Bob might leave the tree a sheepish sound